The invention relates generally to hot gas path components for turbine assemblies and, more particularly, to film cooling of hot gas path components and to secondary cooling between hot gas path components. A variety of components in aircraft engines and stationary power systems are operated in extremely hot environments. These components are exposed to hot gases having temperatures up to 3400 degrees Fahrenheit, for aircraft applications, and up to about 2700 degrees Fahrenheit for stationary power generation applications. To cool the components exposed to the hot gases, these “hot gas path” components typically have both internal and film cooling. For example, a number of cooling holes may extend from a relatively cool surface of the component to a “hot” surface of the component. The hot surface is exposed to the hot gases and thus requires more thermal management than does the relatively cool surface of the component, which may itself be at a temperature of about 1000 to about 1800 degrees Fahrenheit. This technique is known as film cooling. The coolant typically is compressed air bled off the compressor, which is then bypassed around the engine's combustion zone and fed through the cooling holes to the hot surface. The coolant forms a protective “film” between the hot component surface and the hot gas flow, thereby helping protect the component from heating.
Because bleeding the coolant off the compressor reduces the overall efficiency of the engine, it is desirable to improve cooling effectiveness for a given amount of coolant. A number of techniques have been employed to enhance the effectiveness of film cooling, including using “shaped” cooling holes. Film cooling is highest when the coolant flow hugs the hot surface. However, conventional film cooling techniques can be improved to further direct and maintain the coolant flow along the hot surface.
Accordingly, it would be desirable to provide film cooling for hot gas path components with improved cooling effectiveness. More particularly, it would be desirable to further direct and maintain the coolant flow along the hot surface of the gas path component, to enhance the protective “film” effectiveness.